Telephone-receiver



(No Model.)

L. FAIRBANKS. v

TELEPHONE RECEIVER. I E

No. 349,575. Patented Spt. 21, 1886.

MTNEEEEE- R. PErEns. wowuum mr. Washington. ac.

UNITED STATES- PATENT OFFICE.

LORENZO S. FAIRBANKS, OF BOSTON, MASSACHUSETTS.

TELEPH'ONE-RECEIVER.

SPECIFICATION forming part of Letters Patent No. 349,575, dated September 21, 1886.

Application filed January 14,1886. Serial No. 188,607. (No model.)

To all whom it may concern:

Be it known that I, LORENZO S. FAIR- BANKS, of Boston, in the county of Suffolk and Commonwealth of Massachusetts, have invented certain new and useful Improvements in Receiving-Telephones, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, making apart of this specification.

. This invention relates to that class of instruments called magneto-electric telephones, and commonly used as receivers, but capable also of being used as transmitters. Its special distinction lies in its adaptation to overcome or diminish the effects of induction on telephone-lines, as well as in its novel construction to secure superior strength and efficiency.

It consists of a horseshoe magnet of peculiar form, as herein described, and in combination with it a bar-magnet having a polar extension of soft iron, preferably consisting of a bundle of iron wires surrounded by aspool and coil of insulated wire, and a metal diaphragm in proximity to the poles of both magnets, which are adjusted to be in the same plane, or nearly so.

In the accompanying drawings, Figure 1 represents a vertical section of the instrument. Fig. 2 represents a perspective view of the horseshoe-magnet,with cap and binding-posts a a, and of the end of .the inclosed parts.

The magnet is made in the form of a hollow cylinder closed at one end and slit longitudinally through its axis from the open end to the base. The construction of this magnet is not limited to the form shown by Fig. 2. It may be like any ordinary horseshoe-magnet, with only the poles semi-cylindrical or curvilinear, to surround and inclose the central barmagnet.

In Fig. 1,A is a hollow handle with binding-posts a a inserted in the end and through the magnet,insulated fromit by means of tubes of hard rubber.

B is a mouth or car piece fastened to a supporting-cap, O, with the diaphragm D fixed between them. The cap turns upon the handle as a nut with a fine thread, whereby the diaphragm may be readily adjusted at the proper distance from the poles of the magnets.

E is the bar-magnet with a screw upon its lower end, by which it is secured centrally to the base of the horseshoe-magnet, and adjusted as required.

F is a spool carrying a coil of insulated wire, and G is a bundle of fine uncovered iron wires within the tube of the spool, in contact with the pole of the bar-magnet, as a pole-extension of the same.

H is a horseshoe-magnet surrounding or inclosing the spool and bar-magnet. For the bundle of wires used as a pole-extension of the central magnet, a solid piece of soft iron may be substituted, or the bar-magnet may be replaced by a bar of soft iron or a long bundle of wires to form an electro-niagnet, though the construction described is believed to be the best. 7 c

It is evident that in a telephone .thus constructed a very powerful magnetic field is presented to the diaphragm, while the external magnet, by reason of its tubular form, acts upon the diaphragm with reference to its nodes of vibration, controlling the extra or continuing vibrations at points beyond the center in such a manner, in connection with the employment of the central magnet, as to overcome to a great extent, if not perfectly, the annoying effects of induction from neighboring electric circuits hitherto experienced.

Having thus described my invention, what I claim is 1. In a telephone, a magnet, substantially as described, in the form of a hollow cylinder closed at one end and slit from the open end to the base, for the purpose set forth.

2. In a magneto-electric telephone, in connection with a diaphragm, the combination of a magnet made in the form of a hollow cylinder closed at one end and slit longitudinally from the open end to the base, with a barmagnet having a soft-iron pole-extension, preferably a bundle of fine iron wires, surrounded by a coil of insulated wire fixed centrally between the poles of said cylindrical magnet, whereby a strong external magnetic field is produced around the central magnet, substantially as and for the purposes described .and set forth.

3. In a magneto-electric telephone, in com me nection with a. diaphragm, a horseshoe-magcentral magnet, substantially as and for the net having its pole terminating in the form of purposes described and set forth. sect-ions of a hollow cylinder, combined witha bar-magnet surmounted by a helix and core, LORENZO FAIRBANKS the latter being fixed axially between the i Witnesses: poles of the former, to produce a strong addi- T. G. SMITH,

tional magnetic field around the pole of the CARL F. REDWITZ. 

